Does it only appear when the fans are running?
If so, the fan motor bearings may be squeaking and starting to go.
Do this when the engine is cold. Reach in from the front and give each fan a quick spin by hand.
Make sure each fan spins freely and without binding or rubbing on the radiator.
If the fan stops immediately when spun and is not rubbing on the radiator, the bearings may be on the way out. They may also squeak when rotated.
I had one fan motor (left one) years ago that stopped immediately when spun and squeaked when rotated, indicating the fan motor bearings were toast.
I replaced both fan motors, and problem solved.